Lens module

ABSTRACT

A lens module includes a first lens having refractive power; a second lens having refractive power, both surfaces thereof being convex; a third lens having refractive power, both surfaces thereof being concave; a fourth lens having refractive power; a fifth lens having refractive power, an object-side surface thereof being convex; and a sixth lens having refractive power and having one or more inflection points on an image-side surface thereof, an object-side surface thereof being convex. The first to sixth lenses are sequentially disposed in numerical order from the first lens to the sixth lens from an object side of the lens module toward an image side of the lens module.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit under 35 USC 119(a) of Korean Patent Application No. 10-2014-0161135 filed on Nov. 18, 2014, in the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference for all purposes.

BACKGROUND

1. Field

This application relates to a lens module having an optical system including six lenses.

2. Description of Related Art

A lens module mounted in a camera module provided in a mobile communications terminal includes a plurality of lenses. For example, the lens module may include six lenses in order to configure a high-resolution optical system.

However, when a high-resolution optical system is configured using the plurality of lenses as described above, a length (the distance from an object-side surface of a first lens to an image plane) of the optical system may be increased. In this case, it is difficult to mount the lens module in a thin mobile communications terminal.

SUMMARY

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

In one general aspect, a lens module includes a first lens having refractive power; a second lens having refractive power, both surfaces thereof being convex; a third lens having refractive power, both surfaces thereof being concave; a fourth lens having refractive power; a fifth lens having refractive power, an object-side surface thereof being convex; and a sixth lens having refractive power and having one or more inflection points on an image-side surface thereof, an object-side surface thereof being convex; wherein the first to sixth lenses are sequentially disposed in numerical order from the first lens to the sixth lens from an object side of the lens module toward an image side of the lens module.

An object-side surface of the first lens may be convex.

An image-side surface of the first lens may be convex.

An object-side surface of the fourth lens may be convex.

An image-side surface of the fourth lens may be concave.

An object-side surface of the fourth lens may be concave.

An image-side surface of the fourth lens may be convex.

An image-side surface of the fifth lens may be concave.

The image-side surface of the sixth lens may be concave.

In the lens module, |r1/T1|<17.0 may be satisfied, where r1 is a radius of curvature of an object-side surface of the first lens, and T1 is a thickness of the first lens on an optical axis.

In the lens module, |f6/f|<79.0 may be satisfied, where f is an overall focal length of an optical system including the first to sixth lenses, and f6 is a focal length of the sixth lens.

In the lens module, f5/f<−3.0 may be satisfied, where f is an overall focal length of an optical system including the first to sixth lenses, and f5 is a focal length of the fifth lens.

In the lens module, |(r7+r8)/(r7−r8)|<200 may be satisfied, where r7 is a radius of curvature of an object-side surface of the fourth lens, and r8 is a radius of curvature of an image-side surface of the fourth lens.

In the lens module, wherein |n3−n4|<0.1 may be satisfied, where n3 is a refractive index of the third lens, and n4 is a refractive index of the fourth lens.

In another general aspect, a lens module includes a first lens having negative refractive power; a second lens having positive refractive power; a third lens having negative refractive power; a fourth lens having negative refractive power; a fifth lens having negative refractive power; and a sixth lens having negative refractive power and having one or more inflection points on an image-side surface thereof; wherein the first to sixth lenses are sequentially disposed in numerical order from the first lens to the sixth lens from an object side of the lens module toward an image side of the lens module.

In the lens module of claim 15, 5.0<|(r9+r10)/(r9−r10)|<21.0 may be satisfied, where r9 is a radius of curvature of an object-side surface of the fifth lens, and r10 is a radius of curvature of an image-side surface of the fifth lens.

Other features and aspects will be apparent from the following detailed description, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of a first example of a lens module.

FIG. 2 is a graph including curves representing modulation transfer function (MTF) characteristics of the lens module illustrated in FIG. 1.

FIG. 3 is a graph including curves representing aberration characteristics of the lens module illustrated in FIG. 1.

FIG. 4 is a table representing characteristics of the lenses of the lens module illustrated in FIG. 1.

FIG. 5 is a table representing aspherical surface coefficients of the lenses of the lens module illustrated in FIG. 1.

FIG. 6 is a view of a second example of a lens module.

FIG. 7 is a graph including curves representing MTF characteristics of the lens module illustrated in FIG. 6.

FIG. 8 is a graph including curves representing aberration characteristics of the lens module illustrated in FIG. 6.

FIG. 9 is a table representing characteristics of the lenses of the lens module illustrated in FIG. 6.

FIG. 10 is a table representing aspherical surface coefficients of the lenses of the lens module illustrated in FIG. 6.

FIG. 11 is a view of a third example of a lens module.

FIG. 12 is a graph including curves representing MTF characteristics of the lens module illustrated in FIG. 11.

FIG. 13 is a graph including curves representing aberration characteristics of the lens module illustrated in FIG. 11.

FIG. 14 is a table representing characteristics of the lenses of the lens module illustrated in FIG. 11.

FIG. 15 is a table representing aspherical surface coefficients of the lenses of the lens module illustrated in FIG. 11.

FIG. 16 is a view of a fourth example of a lens module.

FIG. 17 is a graph including curves representing MTF characteristics of the lens module illustrated in FIG. 16.

FIG. 18 is a graph including curves representing aberration characteristics of the lens module illustrated in FIG. 16.

FIG. 19 is a table representing characteristics of the lenses of the lens module illustrated in FIG. 16.

FIG. 20 is a table representing aspherical surface coefficients of the lenses of the lens module illustrated in FIG. 16.

FIG. 21 is a view of a fifth example of a lens module.

FIG. 22 is a graph including curves representing MTF characteristics of the lens module illustrated in FIG. 21.

FIG. 23 is a graph including curves representing aberration characteristics of the lens module illustrated in FIG. 21.

FIG. 24 is a table representing characteristics of the lenses of the lens module illustrated in FIG. 21.

FIG. 25 is a table illustrating aspherical surface coefficients of the lenses of the lens module illustrated in FIG. 21.

Throughout the drawings and the detailed description, the same reference numerals refer to the same elements. The drawings may not be to scale, and the relative size, proportions, and depiction of elements in the drawings may be exaggerated for clarity, illustration, and convenience.

DETAILED DESCRIPTION

The following detailed description is provided to assist the reader in gaining a comprehensive understanding of the methods, apparatuses, and/or systems described herein. However, various changes, modifications, and equivalents of the methods, apparatuses, and/or systems described herein will be apparent to one of ordinary skill in the art. The sequences of operations described herein are merely examples, and are not limited to those set forth herein, but may be changed as will be apparent to one of ordinary skill in the art, with the exception of operations necessarily occurring in a certain order. Also, descriptions of functions and constructions that are well known to one of ordinary skill in the art may be omitted for increased clarity and conciseness.

The features described herein may embodied in different forms, and are not to be construed as being limited to the examples described herein. Rather, the examples described herein have been provided so that this disclosure will be thorough and complete, and will convey the full scope of the disclosure to one of ordinary skill in the art.

In this application, a first lens refers to a lens closest to an object (or a subject), while a sixth lens refers to a lens closest to an image plane (or an image sensor). Further, a first surface of each lens refers to a surface thereof closest to an object (or a subject), and a second surface of each lens refers to a surface thereof closest to an image plane (or an image sensor). Further, all of radii of curvature, thicknesses, OALs (optical axis distances from a first surface of the first lens to the image plane), SLs (distances from a stop to the image plane), IMGHs (image heights), and BFLs (back focus lengths) of the lenses, an overall focal length of an optical system, and a focal length of each lens are expressed in millimeters (mm). Further, thicknesses of lenses, gaps between the lenses, OALs, and SLs are distances measured in relation to an optical axis of the lenses. Further, in a description for shapes of the lenses, a statement that one surface of a lens is convex means that an optical axis portion of a corresponding surface is convex, and a statement that one surface of a lens is concave means that an optical axis portion of a corresponding surface is concave. Therefore, although it may be described that one surface of a lens is convex, an edge portion of the lens may be concave. Likewise, although it may be described that one surface of a lens is concave, an edge portion of the lens may be convex.

A lens module includes an optical system including a plurality of lenses. As an example, the optical system of the lens module may include six lenses having refractive power. However, the lens module is not limited thereto. For example, the lens module may include other components that do not have refractive power. As an example, the lens module may include a stop controlling an amount of light. As another example, the lens module may further include an infrared cut-off filter filtering infrared light. As another example, the lens module may further include an image sensor (that is, an imaging device) converting an image of a subject incident thereon through the optical system into electrical signals. As another example, the lens module may further include a gap maintaining member adjusting a gap between lenses.

First to sixth lenses may be formed of materials having a refractive index different from that of air. For example, the first to sixth lenses may be formed of plastic or glass. At least one of the first to sixth lenses may have an aspherical surface shape. As an example, only the sixth lens of the first to sixth lenses may have an aspherical surface shape. As another example, at least one surface of all of the first to sixth lenses may be aspherical. Here, the aspherical surface of each lens may be represented by the following Equation 1:

$\begin{matrix} {Z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {Ar}^{4} + {Br}^{6} + {Cr}^{8} + {Dr}^{10} + {Er}^{12} + {Fr}^{14} + {Gr}^{16} + {Hr}^{18} + {Jr}^{20}}} & (1) \end{matrix}$

Here, c is an inverse of a radius of curvature of a corresponding lens, k is a conic constant, and r is a distance from a certain point on an aspherical surface to an optical axis in a direction perpendicular to the optical axis. In addition, constants A to J are respectively 4-th order to 20-th order aspherical surface coefficients. In addition, Z is a distance between the certain point on the aspherical surface at the distance r and a tangential plane meeting the apex of the aspherical surface of the lens.

The lens module may have a wide field of view (FOV) of 74° or more. Therefore, the lens module may easily photograph a wide background or object.

The optical system of the lens module satisfies the following Conditional Expression: |r1/T1|<17.0.

Here, r1 is a radius of curvature in mm of an object-side surface of the first lens, and T1 is a thickness in mm of the first lens at an optical axis portion.

The above Conditional Expression is a condition for optimizing manufacturing of the first lens. For example, in a case in which |r1/T1| is out of an upper limit value of the above Conditional Expression, it may not be easy to make the first lens thin. In addition, in the case in which |r1/T1| is out of the upper limit value of the above Conditional Expression, it may be difficult for the first lens to realize high resolution.

Meanwhile, the above Conditional Expression may also be optimized in the following numerical range: 5.0<|r1/T1|<17.0.

The optical system of the lens module also satisfies the following Conditional Expression: |f6/f|<79.0.

Here, f is an overall focal length in mm of the optical system including the first to sixth lenses, and f6 is a focal length in mm of the sixth lens.

The above Conditional Expression is a condition for optimizing an aberration correction effect by the sixth lens. For example, in a case in which |f6/f| is out of an upper limit value of the above Conditional Expression, the sixth lens has excessively high refractive power, and thus it may not effectively correct aberration of the optical system.

Meanwhile, the above Conditional Expression may also be optimized in the following numerical range: 3.0<|f6/f|<82.0.

The optical system of the lens module also satisfies the following Conditional Expression: f5/f<−3.0.

Here, f is an overall focal length in mm of the optical system including the first to sixth lenses, and f5 is a focal length in mm of the fifth lens.

The above Conditional Expression is a condition for optimizing an aberration correction effect by the fifth lens. For example, in a case in which f5/f is out of an upper limit value of the above Conditional Expression, the fifth lens may not effectively correct aberration. Conversely, in a case in which the above Conditional Expression is satisfied, the fifth lens has an excellent aberration correction effect and improves resolution of the lens module.

Meanwhile, the above Conditional Expression may also be optimized in the following numerical range: f5/f<−30.0.

The optical system of the lens module also satisfies the following Conditional Expression: |(r7+r8)/(r7−r8)|<200.

Here, r7 is a radius of curvature in mm of an object-side surface of the fourth lens, and r8 is a radius of curvature in mm of an image-side surface of the fourth lens.

The above Conditional Expression is a condition for optimizing an aberration correction effect by the fourth lens. For example, in a case in which |(r7+r8)/(r7−r8)| is out of an upper limit value of the above Conditional Expression, the fourth lens may not effectively correct aberration. Conversely, in a case in which the above Conditional Expression is satisfied, the fourth lens has an excellent aberration correction effect and improves resolution of the lens module.

Meanwhile, the above Conditional Expression may also be optimized in the following numerical range: 2.0<|(r7+r8)/(r7−r8)|<200.

The optical system of the lens module also satisfies the following Conditional Expression: |n3−n4|<0.10.

Here, n3 is a refractive index of the third lens, and n4 is a refractive index of the fourth lens.

The above Conditional Expression is a condition for optimizing materials of the third and fourth lenses. For example, in a case in which |n3−n4| is out of an upper limit value of the above Conditional Expression, an aberration correction effect of the third and fourth lenses may be insufficient. Conversely, in a case in which the above Conditional Expression is satisfied, an aberration correction effect of the third and fourth lenses is excellent and a cost required for manufacturing the third and fourth lenses is low.

The lens module may be manufactured in the following form.

As an example, the optical system of the lens module includes a first lens having refractive power; a second lens having refractive power, both surfaces thereof being convex; a third lens having refractive power, both surfaces thereof being concave; a fourth lens; a fifth lens having refractive power, an object-side surface thereof being convex; and a sixth lens having refractive power, an object-side surface thereof being convex.

As another example, the optical system of the lens module includes a first lens having negative refractive power; a second lens having positive refractive power; a third lens having negative refractive power; a fourth lens having negative refractive power; a fifth lens having negative refractive power; and a sixth lens having negative refractive power.

Next, the main components of the lens module will be described.

The first lens may have refractive power. For example, the first lens may have negative refractive power.

The first lens may have a meniscus shape. As an example, the first lens may have a meniscus shape of which an object-side surface is convex or a meniscus shape of which an image-side surface is convex.

The first lens may have an aspherical surface. For example, both surfaces of the first lens may be aspherical. The first lens may be formed of a material having high light transmissivity and excellent workability. For example, the first lens may be formed of plastic. However, a material of the first lens is not limited to plastic. For example, the first lens may be formed of glass.

The second lens may have refractive power. For example, the second lens may have positive refractive power.

Both surfaces of the second lens may be convex. As an example, a first surface of the second lens may be convex and a second surface thereof may be convex.

The second lens may have an aspherical surface. For example, both surfaces of the second lens may be aspherical. The second lens may be formed of a material having high light transmissivity and excellent workability. For example, the second lens may be formed of plastic. However, a material of the second lens is not limited to plastic. For example, the second lens may be formed of glass. The second lens may be formed of a material having a high refractive index. For example, the second lens may be formed of a material having a refractive index of 1.60 or more (in this case, the second lens may have an Abbe number of 30 or less). The second lens formed of this material may easily refract light even when having a small curvature shape. Therefore, the second lens formed of this material may be easily manufactured and be advantageous in lowering a defect rate depending on a manufacturing tolerance. In addition, the second lens formed of this material may decrease a distance between lenses, and thus it may be advantageous in miniaturizing the lens module.

The third lens may have refractive power. For example, the third lens may have negative refractive power.

Both surfaces of the third lens may be concave. As an example, a first surface of the third lens may be concave and a second surface thereof may be concave.

The third lens may have an aspherical surface. For example, both surfaces of the third lens may be aspherical. The third lens may be formed of a material having high light transmissivity and excellent workability. For example, the third lens may be formed of plastic. However, a material of the third lens is not limited to plastic. For example, the third lens may be formed of glass.

The fourth lens may have refractive power. For example, the fourth lens may have negative refractive power.

The fourth lens may have a meniscus shape. For example, the fourth lens may have a meniscus shape of which an object-side surface is convex or a meniscus shape of which an image-side surface is convex.

The fourth lens may have an aspherical surface. For example, both surfaces of the fourth lens may be aspherical. The fourth lens may be formed of a material having high light transmissivity and excellent workability. For example, the fourth lens may be formed of plastic. However, a material of the fourth lens is not limited to plastic. For example, the fourth lens may be formed of glass.

The fifth lens may have refractive power. For example, the fifth lens may have negative refractive power.

The fifth lens may be substantially convex toward the object side. As an example, a first surface of the fifth lens may be convex and a second surface thereof may be concave.

The fifth lens may have one or more inflection points. As an example, the fifth lens may have one or more inflection points formed on a first surface thereof. As another example, the fifth lens may have one or more inflection points formed on a second surface thereof. The fifth lens configured as described above may be convex toward the object side at an optical axis portion and be concave at an edge portion.

The fifth lens may have an aspherical surface. For example, both surfaces of the fifth lens may be aspherical. The fifth lens may be formed of a material having high light transmissivity and excellent workability. For example, the fifth lens may be formed of plastic. However, a material of the fifth lens is not limited to plastic. For example, the fifth lens may be formed of glass.

The fifth lens may be formed of a material having a high refractive index. For example, the fifth lens may be formed of a material having a refractive index of 1.60 or more (in this case, the fifth lens may have an Abbe number of 30 or less). The fifth lens formed of this material may easily refract light even when having a small curvature shape. Therefore, the fifth lens formed of this material may be easily manufactured and be advantageous in lowering a defect rate depending on a manufacturing tolerance. In addition, the fifth lens formed of this material may decrease a distance between lenses, and thus it may be advantageous in miniaturizing the lens module.

The fifth lens may satisfy the following Conditional Expression. The fifth lens satisfying the following Conditional Expression may be easily manufactured. 5.0<|(r9+r10)/(r9−r10)|<21.0

Here, r9 is a radius of curvature of an object-side surface of the fifth lens, and r10 is a radius of curvature of an image-side surface of the fifth lens.

The sixth lens may have refractive power. For example, the sixth lens may have positive or negative refractive power.

The sixth lens may have a meniscus shape of which an object-side surface is convex. As an example, a first surface of the sixth lens may be convex, and a second surface thereof may be concave.

The sixth lens may include an inflection point. For example, the first surface of the sixth lens may be convex at the center of an optical axis, concave in the vicinity of the optical axis, and convex at an edge thereof. Likewise, the second surface of the sixth lens may be concave at the center of an optical axis and become convex at an edge thereof.

The sixth lens may have an aspherical surface. For example, both surfaces of the sixth lens may be aspherical. The sixth lens may be formed of a material having high light transmissivity and high workability. For example, the sixth lens may be formed of plastic. However, a material of the sixth lens is not limited to plastic. For example, the sixth lens may be formed of glass.

The image sensor may be configured to realize a high resolution of 1300 megapixels. For example, a unit size of the pixels of the image sensor may be 1.12 μm or less.

The lens module may be configured to have a wide field of view. For example, the optical system of the lens module may have a field of view of 74° or more. In addition, the lens module may have a relatively short length (OAL). For example, an overall length (distance from the object-side surface of the first lens to the image plane) of the optical system configuring the lens module may be 4.30 mm or less. Therefore, the lens module may be advantageously miniaturized.

FIG. 1 is a view of a first example of a lens module.

A lens module 100 includes an optical system including a first lens 110, a second lens 120, a third lens 130, a fourth lens 140, a fifth lens 150, and a sixth lens 160. In addition, the lens module 100 further includes an infrared cut-off filter 70 and an image sensor 80. Further, the lens module 100 may further include a stop (ST) (not shown). For example, the stop may be disposed between a subject (object) and the first lens 110.

In this example, the first lens 110 has negative refractive power, and an object-side surface thereof is convex and an image-side surface thereof is concave. The second lens 120 has positive refractive power, and an object-side surface thereof is convex and an image-side surface thereof is convex. The third lens 130 has negative refractive power, and an object-side surface thereof is concave and an image-side surface thereof is concave. The fourth lens 140 has negative refractive power, and an object-side surface thereof is convex and an image-side surface thereof is concave. The fifth lens 150 has negative refractive power, and an object-side surface thereof is convex and an image-side surface thereof is concave. In addition, one or more inflection points are formed on each of the object-side surface and the image-side surface of the fifth lens. The sixth lens 160 has negative refractive power, and an object-side surface thereof is convex and an image-side surface thereof is concave. In addition, one or more inflection points are formed on each of the object-side surface and the image-side surface of the sixth lens.

In this example, all of the first lens 110, the third lens 130, the fourth lens 140, the fifth lens 150, and the sixth lens 160 have negative refractive power as described above. Among these lenses, the fifth lens 150 has the strongest refractive power, and the third lens 130 has the weakest refractive power.

FIG. 2 is a graph including curves representing MTF characteristics of the lens module illustrated in FIG. 1.

FIG. 3 is a graph including curves representing aberration characteristics of the lens module illustrated in FIG. 1.

FIG. 4 is a table representing characteristics of the lenses of the lens module illustrated in FIG. 1. In FIG. 4, Surface Nos. 1 and 2 indicate the first surface (object-side surface) and the second surface (image-side surface) of the first lens, and Surface Nos. 3 and 4 indicate the first and second surfaces of the second lens. Similarly, Surface Nos. 5 to 12 indicate first and second surfaces of the third to sixth lenses, respectively. In addition, Surface Nos. 13 and 14 indicate first and second surfaces of the infrared cut-off filter.

FIG. 5 is a table representing aspherical surface coefficients of the lenses of lens module illustrated in FIG. 1. In FIG. 5, the labels of the columns are Surface Nos. of the first to sixth lenses, and the labels of the rows are characteristics corresponding to each surface of the lenses.

FIG. 6 is a view of a second example of a lens module.

A lens module 200 includes an optical system including a first lens 210, a second lens 220, a third lens 230, a fourth lens 240, a fifth lens 250, and a sixth lens 260. In addition, the lens module 200 further includes an infrared cut-off filter 70 and an image sensor 80. Further, the lens module 200 may further include a stop (ST) (not shown). For example, the stop may be disposed between a subject (object) and the first lens.

In this example, the first lens 210 has negative refractive power, and an object-side surface thereof is concave and an image-side surface thereof is convex. The second lens 220 has positive refractive power, and an object-side surface thereof is convex and an image-side surface thereof is convex. The third lens 230 has negative refractive power, and an object-side surface thereof is concave and an image-side surface thereof is concave. The fourth lens 240 has negative refractive power, and an object-side surface thereof is convex and an image-side surface thereof is concave. The fifth lens 250 has negative refractive power, and an object-side surface thereof is convex and an image-side surface thereof is concave. In addition, one or more inflection points are formed on each of the object-side surface and the image-side surface of the fifth lens. The sixth lens 260 has negative refractive power, and an object-side surface thereof is convex and an image-side surface thereof is concave. In addition, one or more inflection points are formed on each of the object-side surface and the image-side surface of the sixth lens.

In this example, all of the first lens 210, the third lens 230, the fourth lens 240, the fifth lens 250, and the sixth lens 260 have negative refractive power as described above. Among these lenses, the fifth lens 250 has the strongest refractive power, and the third lens 230 has the weakest refractive power.

FIG. 7 is a graph including curves representing MTF characteristics of the lens module illustrated in FIG. 6.

FIG. 8 is a graph including curves representing aberration characteristics of the lens module illustrated in FIG. 6.

FIG. 9 is a table representing characteristics of the lenses of the lens module illustrated in FIG. 6. In FIG. 9, Surface Nos. 1 and 2 indicate the first surface (object-side surface) and the second surface (image-side surface) of the first lens, and Surface Nos. 3 and 4 indicate the first and second surfaces of the second lens. Similarly, Surface Nos. 5 to 12 indicate first and second surfaces of the third to sixth lenses, respectively. In addition, Surface Nos. 13 and 14 indicate first and second surfaces of the infrared cut-off filter.

FIG. 10 is a table representing aspherical surface coefficients of the lenses of the lens module illustrated in FIG. 6. In FIG. 10, the labels of the columns are Surface Nos. of the first to sixth lenses, and the labels of the rows are characteristics corresponding to each surface of the lenses.

FIG. 11 is a view of a third example of a lens module.

A lens module 300 includes an optical system including a first lens 310, a second lens 320, a third lens 330, a fourth lens 340, a fifth lens 350, and a sixth lens 360. In addition, the lens module 300 further includes an infrared cut-off filter 70 and an image sensor 80. Further, the lens module 300 may further include a stop (ST) (not shown). For example, the stop may be disposed between a subject (object) and the first lens.

In this example, the first lens 310 has negative refractive power, and an object-side surface thereof is concave and an image-side surface thereof is convex. The second lens 320 has positive refractive power, and an object-side surface thereof is convex and an image-side surface thereof is convex. The third lens 330 has negative refractive power, and an object-side surface thereof is concave and an image-side surface thereof is concave. The fourth lens 340 has negative refractive power, and an object-side surface thereof is convex and an image-side surface thereof is concave. The fifth lens 350 has negative refractive power, and an object-side surface thereof is convex and an image-side surface thereof is concave. In addition, one or more inflection points are formed on each of the object-side surface and the image-side surface of the fifth lens. The sixth lens 360 has negative refractive power, and an object-side surface thereof is convex and an image-side surface thereof is concave. In addition, one or more inflection points are formed on each of the object-side surface and the image-side surface of the sixth lens.

In this example, all of the first lens 310, the third lens 330, the fourth lens 340, the fifth lens 350, and the sixth lens 360 have negative refractive power as described above. Among these lenses, the fourth lens 340 has the strongest refractive power, and the third lens 330 has the weakest refractive power.

FIG. 12 is a graph including curves representing MTF characteristics of the lens module illustrated in FIG. 11.

FIG. 13 is a graph including curves representing aberration characteristics of the lens module illustrated in FIG. 11.

FIG. 14 is a table representing characteristics of the lenses of the lens module illustrated in FIG. 11. In FIG. 14, Surface Nos. 1 and 2 indicate the first surface (object-side surface) and the second surface (image-side surface) of the first lens, and Surface Nos. 3 and 4 indicate the first and second surfaces of the second lens. Similarly, Surface Nos. 5 to 12 indicate first and second surfaces of the third to sixth lenses, respectively. In addition, Surface Nos. 13 and 14 indicate first and second surfaces of the infrared cut-off filter.

FIG. 15 is a table representing aspherical surface coefficients of the lenses of the lens module illustrated in FIG. 11. In FIG. 15, the labels of the columns are Surface Nos. of the first to sixth lenses, and the labels of the rows are characteristics corresponding to each surface of the lenses.

FIG. 16 is a view of a fourth example of a lens module.

A lens module 400 includes an optical system including a first lens 410, a second lens 420, a third lens 430, a fourth lens 440, a fifth lens 450, and a sixth lens 460. In addition, the lens module 400 further includes an infrared cut-off filter 70 and an image sensor 80. Further, the lens module 400 may further include a stop (ST) (not shown). For example, the stop may be disposed between a subject (object) and the first lens.

In this example, the first lens 410 has negative refractive power, and an object-side surface thereof is concave and an image-side surface thereof is convex. The second lens 420 has positive refractive power, and an object-side surface thereof is convex and an image-side surface thereof is convex. The third lens 430 has negative refractive power, and an object-side surface thereof is concave and an image-side surface thereof is concave. The fourth lens 440 has negative refractive power, and an object-side surface thereof is concave and an image-side surface thereof is convex. The fifth lens 450 has negative refractive power, and an object-side surface thereof is convex and an image-side surface thereof is concave. In addition, one or more inflection points are formed on each of the object-side surface and the image-side surface of the fifth lens. The sixth lens 460 has negative refractive power, and an object-side surface thereof is convex and an image-side surface thereof is concave. In addition, one or more inflection points are formed on each of the object-side surface and the image-side surface of the sixth lens.

In this example, all of the first lens 410, the third lens 430, the fourth lens 440, the fifth lens 450, and the sixth lens 460 have negative refractive power as described above. Among these lenses, the fourth lens 440 has the strongest refractive power, and the third lens 430 has the weakest refractive power.

FIG. 17 is a graph including curves representing MTF characteristics of the lens module illustrated in FIG. 16.

FIG. 18 is a graph including curves representing aberration characteristics of the lens module illustrated in FIG. 16.

FIG. 19 is a table representing characteristics of the lenses of the lens module illustrated in FIG. 16. In FIG. 19, Surface Nos. 1 and 2 indicate the first surface (object-side surface) and the second surface (image-side surface) of the first lens, and Surface Nos. 3 and 4 indicate the first and second surfaces of the second lens. Similarly, Surface Nos. 5 to 12 indicate first and second surfaces of the third to sixth lenses, respectively. In addition, Surface Nos. 13 and 14 indicate first and second surfaces of the infrared cut-off filter.

FIG. 20 is a table representing aspherical surface coefficients of the lenses of the lens module illustrated in FIG. 16. In FIG. 20, the labels of the columns are Surface Nos. of the first to sixth lenses, and the labels of the rows are characteristics corresponding to each surface of the lenses.

FIG. 21 is a view of a fifth example of a lens module.

A lens module 500 includes an optical system including a first lens 510, a second lens 520, a third lens 530, a fourth lens 540, a fifth lens 550, and a sixth lens 560. In addition, the lens module 500 further includes an infrared cut-off filter 70 and an image sensor 80. Further, the lens module 500 may further include a stop (ST) (not shown). For example, the stop may be disposed between a subject (object) and the first lens.

In this example, the first lens 510 has negative refractive power, and an object-side surface thereof is concave and an image-side surface thereof is convex. The second lens 520 has positive refractive power, and an object-side surface thereof is convex and an image-side surface thereof is convex. The third lens 530 has negative refractive power, and an object-side surface thereof is concave and an image-side surface thereof is concave. The fourth lens 540 has negative refractive power, and an object-side surface thereof is convex and an image-side surface thereof is concave. The fifth lens 550 has negative refractive power, and an object-side surface thereof is convex and an image-side surface thereof is concave. In addition, one or more inflection points are formed on each of the object-side surface and the image-side surface of the fifth lens. The sixth lens 560 has negative refractive power, and an object-side surface thereof is convex and an image-side surface thereof is concave. In addition, one or more inflection points are formed on each of the object-side surface and the image-side surface of the sixth lens.

In this example, all of the first lens 510, the third lens 530, the fourth lens 540, the fifth lens 550, and the sixth lens 560 have negative refractive power as described above. Among these lenses, the fourth lens 540 has the strongest refractive power, and the third lens 530 has the weakest refractive power.

FIG. 22 is a graph including curves representing MTF characteristics of the lens module illustrated in FIG. 21.

FIG. 23 is a graph including curves representing aberration characteristics of the lens module illustrated in FIG. 21.

FIG. 24 is a table representing characteristics of the lenses of the lens module illustrated in FIG. 21. In FIG. 24, Surface Nos. 1 and 2 indicate the first surface (object-side surface) and the second surface (image-side surface) of the first lens, and Surface Nos. 3 and 4 indicate the first and second surfaces of the second lens. Similarly, Surface Nos. 5 to 12 indicate first and second surfaces of the third to sixth lenses, respectively. In addition, Surface Nos. 13 and 14 indicate first and second surfaces of the infrared cut-off filter.

FIG. 25 is a table representing aspherical surface coefficients of the lenses of lens module illustrated in FIG. 21. In FIG. 25, the labels of the columns are Surface Nos. of the first to sixth lenses, and the labels of the rows are characteristics corresponding to each surface of the lenses.

The following Table 1 lists optical characteristics of the lens modules of the first to fifth examples. The lens module has an overall focal length (f) of 2.70 to 2.80. A focal length (f1) of the first lens is determined in a range of −18.40 to −13.10. A focal length (f2) of the second lens is determined in a range of 1.80 to 1.90. A focal length (f3) of the third lens is determined in a range of −5.30 to −3.90. A focal length (f4) of the fourth lens is determined in a range of −6140 to −11.0. A focal length (f5) of the fifth lens is determined in a range of −1700 to −10.0. A focal length (f6) of the sixth lens is determined in a range of −220 to −10.

TABLE 1 First Second Third Fourth Fifth Remarks Example Example Example Example Example f (EFL) 2.7370 2.7220 2.7330 2.7720 2.7590 f1 −18.418 −13.230 −13.925 −16.185 −13.145 f2 1.8686 1.8723 1.8416 1.8591 1.8510 f3 −5.0998 −5.2522 −4.2506 −4.0168 −5.0310 f4 −22.40 −11.89 −4706.89 −6139.06 −100.03 f5 −99.82 −1698.86 −98.30 −270.54 −10.01 f6 −13.076 −218.931 −17.014 −18.627 35.949 TTL 4.2290 4.3750 3.9570 3.9290 3.9790 FOV 76.00 74.00 74.00 80.00 80.00

The following Table 2 lists values of Conditional Expressions of the lens modules of the first to fifth examples.

TABLE 2 Conditional First Second Third Fourth Fifth Expressions Example Example Example Example Example |r1/T1| 16.945 7.973 16.305 15.747 13.165 |f6/f| 4.778 79.385 6.225 6.720 13.030 f5/f −36.472 −624.122 −35.968 −97.599 −3.628 |(r7 + r8)/ 3.051 1.422 120.010 194.663 9.190 (r7 − r8)| |n3 − n4| 0.000 0.000 0.070 0.070 0.000

As seen in Table 2, the lens modules of the first to fifth examples satisfy all of the Conditional Expressions.

In the examples described above, the optical system has a high resolution.

While this disclosure includes specific examples, it will be apparent to one of ordinary skill in the art that various changes in form and details may be made in these examples without departing from the spirit and scope of the claims and their equivalents. The examples described herein are to be considered in a descriptive sense only, and not for purposes of limitation. Descriptions of features or aspects in each example are to be considered as being applicable to similar features or aspects in other examples. Suitable results may be achieved if the described techniques are performed in a different order, and/or if components in a described system, architecture, device, or circuit are combined in a different manner, and/or replaced or supplemented by other components or their equivalents. Therefore, the scope of the disclosure is defined not by the detailed description, but by the claims and their equivalents, and all variations within the scope of the claims and their equivalents are to be construed as being included in the disclosure. 

What is claimed is:
 1. A lens module comprising: a first lens having refractive power; a second lens having refractive power, both surfaces thereof being convex; a third lens having refractive power, both surfaces thereof being concave; a fourth lens having refractive power; a fifth lens having refractive power, an object-side surface thereof being convex; and a sixth lens having refractive power and having one or more inflection points on an image-side surface thereof, an object-side surface thereof being convex; wherein the first to sixth lenses are sequentially disposed in numerical order from the first lens to the sixth lens from an object side of the lens module toward an image side of the lens module; an object-side surface of the fourth lens is convex, or an image-side surface of the fourth lens is concave; and an image-side surface of the first lens is convex, or an object-side surface of the fourth lens is concave, or an image-side surface of the fifth lens is concave.
 2. The lens module of claim 1, wherein an object-side surface of the first lens is convex.
 3. The lens module of claim 1, wherein the image-side surface of the first lens is convex.
 4. The lens module of claim 1, wherein the object-side surface of the fourth lens is convex.
 5. The lens module of claim 1, wherein the image-side surface of the fourth lens is concave.
 6. The lens module of claim 1, wherein the object-side surface of the fourth lens is concave.
 7. The lens module of claim 1, wherein an image-side surface of the fourth lens is convex.
 8. The lens module of claim 1, wherein the image-side surface of the fifth lens is concave.
 9. The lens module of claim 1, wherein the image-side surface of the sixth lens is concave.
 10. The lens module of claim 1, wherein |r1/T1|<17.0 is satisfied, where r1 is a radius of curvature of an object-side surface of the first lens, and T1 is a thickness of the first lens on an optical axis.
 11. The lens module of claim 1, wherein |f6/f|<79.0 is satisfied, where f is an overall focal length of an optical system comprising the first to sixth lenses, and f6 is a focal length of the sixth lens.
 12. The lens module of claim 1, wherein f5/f<−3.0 is satisfied, where f is an overall focal length of an optical system comprising the first to sixth lenses, and f5 is a focal length of the fifth lens.
 13. The lens module of claim 1, wherein |(r7+r8)/(r7−R8)|<200 is satisfied, where r7 is a radius of curvature of an object-side surface of the fourth lens, and r8 is a radius of curvature of an image-side surface of the fourth lens.
 14. The lens module of claim 1, wherein |n3−n4|<0.1 is satisfied, where n3 is a refractive index of the third lens, and n4 is a refractive index of the fourth lens.
 15. A lens module comprising: a first lens having negative refractive power; a second lens having positive refractive power; a third lens having negative refractive power; a fourth lens having negative refractive power; a fifth lens having negative refractive power; and a sixth lens having negative refractive power and having one or more inflection points on an image-side surface thereof; wherein the first to sixth lenses are sequentially disposed in numerical order from the first lens to the sixth lens from an object side of the lens module toward an image side of the lens module.
 16. The lens module of claim 15, wherein 5.0<|(r9+r10)/(r9−r10)|<21.0 is satisfied, where r9 is a radius of curvature of an object-side surface of the fifth lens, and r10 is a radius of curvature of an image-side surface of the fifth lens. 